Frostless heat pump having thermal expansion valves

Abstract

A heat pump system having an operable relationship for transferring heat between an exterior atmosphere and an interior atmosphere via a fluid refrigerant and further having a compressor, an interior heat exchanger, an exterior heat exchanger, a heat pump reversing valve, an accumulator, a thermal expansion valve having a remote sensing bulb disposed in heat transferable contact with the refrigerant piping section between said accumulator and said reversing valve, an outdoor temperature sensor, and a first means for heating said remote sensing bulb in response to said outdoor temperature sensor thereby opening said thermal expansion valve to raise suction pressure in order to mitigate defrosting of said exterior heat exchanger wherein said heat pump continues to operate in a heating mode.

Description

BACKGROUND OF INVENTIONHeat pumps are well known and used for heating and / or cooling enclosures such as buildings and the like. A heat pump generally includes a heat exchanger fluid (usually called a refrigerant) that is circulated between an interior heat exchanger inside the enclosure and an exterior heat exchanger outside the enclosure.During normal heating mode operation of a heat pump, the exterior (outdoor) heat exchanger thereof becomes colder than exterior ambient and absorbs heat into the refrigerant therefrom, and the interior (indoor) heat exchanger becomes warmer than interior ambient, transferring heat from the refrigerant into the indoor air. Thus, heat is "pumped" from a cooler exterior ambient into an interior ambient.When the exterior temperature is near or below the freezing point of water, generally in the range of 30 to 40 degrees Fahrenheit, ice (frost) usually builds up on the exterior heat exchanger, greatly reducing the heat pump performance. Therefore, defro...

AI Technical Summary

Benefits of technology

Irrespective of the need for defrosting, when the outdoor temperature sensor 35 senses the ambient temperature in the range of 30 to 40.degree. F., the thermal switch inside the control box 30 will turn on the first means for heating 18", likely a small wattage (e.g., 6 Watts or so) electric resistance heater, to heat the remote sensing bulb 48 of the thermal expansion valve 22. The remote sensing bulb 48 will then open the TXV 22-wider than it will open normally. The added heat enables the TXV 22 to operate as if the suction temperature is higher than it actually is, and thus increases refrigerant 17 mass flow rate and evaporator coil 14 temperature for frost mitigation. When the ambient temperature is outside the 30 to 40.degree. F. range, the TXV will function normally. The first means for heating 18" does not require the conventional heat pump defrost control system, typically time/temperature controlled, to be calling for defrost mode operation.

Optionally, if the conventional heat pump defrost control system calls for

Problems solved by technology

When the exterior temperature is near or below the freezing point of water, generally in the range of 30 to 40 degrees Fahrenheit, ice (frost) usually builds up on the exterior heat exchanger, greatly reducing the heat pump performance.

During these outdoor conditions, heat pumps u

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